RIVERS

RIVERS

Processes
1. Solution
  1. Small rocks are dissolved by weak acids
2. Abrasion
  1. Rocks wear down the river bed
3. Attrition
  1. Rocks get smaller by hitting each other
4. Hydraulic action
  1. Water traps air in cracks and weakens the bank
5. Traction
  1. Rocks roll along the river bed
6. Saltation
  1. Rocks bounce along the river bed
7. Suspension
  1. Rocks float along the river
8. Deposition
  1. The river drops its load
Drainage basin
1. Source
  1. Where the river starts
2. Tributary
  1. A small river
3. Confluence
  1. Where two tributaries meet
4. Channel
  1. Where the water flows
5. Meander
  1. A bend in the river
6. Mouth
  1. Where the river meets the sea
7. Floodplain
  1. The area around a river that can flood
8. Watershed
  1. Where all precipitation that lands in the area flows into the river
River long and landforms
1. Changes downstream
  1. Upper course
    1. Steep
    2. Narrow
    3. Rockey
    4. Waterfalls
    5. Slow
    6. Shallow
  2. Middle course
    1. Wider
    2. Deeper
    3. Meanders
    4. Deposition
    5. Rapids
  3. Lower course
    1. Wide
    2. Deep
    3. Ends at the sea
2. Landforms
  1. Meanders
    1. A bend in the river
    2. A lateral formation
    3. Found in the middle course
  2. Oxbow lakes
    1. Luck mere
    2. Where a meander joins and leaves a circular trench
    4. Found in the middle course
  3. V-shaped valleys and interlocking spurs
    1. Resistant rock left behind after erosion
      1. The V-shaped valley cuts down deep into the rock leaving a V-shaped cross section
      2. Interlocking spurs are where a V-shaped valley meanders around hard rock leaving interlocking rocks
    2. Found in the upper course
    3. The River Severn
  4. Rapids
    1. Found in the upper course and the middle course of the river
    2. Formed when fast waters move over hard and soft rock
  5. Waterfalls
    1. Found in the upper course of the river
    2. Niagera falls
    3. Formed by water falling off a cliff and undercutting the cliff to form a platform that falls and retreats
  6. Gorges
    1. A narrow and steep shaped valley
    2. Found in the upper course of the river
    3. Formed when a waterfall retreats
    4. Cheddar gorge
  7. Floodplains
    1. The area of land where the river floods
    2. Found in the middle course and the lower course of the river
    3. Glouster
  8. Levees
    2. Natural barriers that build over time and help lower the risk of flooding
    3. Found in the middle course and the lower course of the river
    4. Glouster
River flooding
1. Flood Hydrographs
  2. The discharge is the amount of water in the river channel at a certain point along the river
  3. The lag time is the amount of time between the peak rainfall and the peak discharge
2. Flood management stratagies
  1. Hard engineering
    1. Flood walls
      1. Simple walls built around rivers to prevent overflowing
    2. Man made levee
      1. Levees form naturally over time and multiple floods. A man made levee just speeds up the process and doesn't need floods to be built
    3. Sand bags
      1. Placing sandbags around rivers absorbs both water its energy. They are cheap but only work for small floods
    4. Re-routing rivers
      1. Digging a new path to redirect rivers can help by both leading them away form human inhabited areas and making a wider channel for more water to fit in
    5. Dams
      1. Dams take a lot of work and money to build but are often effective once they are. They involve creating a reservoir by flooding an area and then building a large wall that slowly allows the water to fall at a rate that the river can hold.
  2. Soft engineering
    1. Tree planting
      1. Tree planting helps by holding ground together to strengthen the soil (less erosion from the river) and sucking up water so the river can take in more
    2. Dredging
      1. Digging out areas to help the river hold more water
    3. Flood water punping
      1. Building pipes in areas prone to flooding to pump water away when there is a flood
    4. Floodplain zoning
      1. Mapping out areas that are likely to flood and not building settlements in those areas
  3. Case study
    1. Cockermouth
      1. Location: Cumbria, North-West of England
        On the confluence of the River Cocker as it joins River Derwent
        The area is a Site of Special Scientific Interest (SSSI)
      2. A big flood in November 2009 with water levels at 2.5 meters cost £276 million in damage
      3. 2013 flood defence scheme
        Self-closing barriers which only close when the river floods
        A 180 meter embankment
        Flood proofing for existing properties
        Eight new flood gates
        Cost £4.4 million to complete
        It has little impact on the environment and preserves the historical surroundings
        The scheme alerts people by text or email when the barriers start to rise so preparations and evacuations can begin

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	Created by Amy Taylor about 4 years ago